Toothed power transmission belts have a polymeric body such as a rubber, thermoplastic, or urethane, with a plurality of teeth or cogs formed along at least one side or both sides of such belts. A tensile member is typically embedded in the body as a tensile load-carrying member.
It is preferred to have the belt teeth reinforced with a material to enhance their shear strength and wear-resistance, or to alter their coefficient of friction for engagement with a toothed pulley. The material generally comprises fabrics of a woven type such as a canvas, a crimped stretchable nylon, and a leno-weave, etc., and may be of a knit fabric such as a 1×1 rib knit. Such fabrics are disposed in the belt at a peripheral surface that includes the belt teeth and may be in the form of a single layer fabric, multiple layers of woven fabrics, or bonded layers of fabrics.
During operation, the fabric reinforcement wears creating dust and debris particles. The dust and debris is detrimental to the operation of adjacent components and may interfere with operation of certain types of equipment over time. For example, printers, copiers and cameras to name a few. Further, the dust and debris particles from the prior art belts may be electrically conductive, depending upon the belt materials. Depending upon the application, it is not desirable to have electrically conductive materials coating components in electrical equipment.
Belts are also taught with fabric jackets having an outer layering of impervious thermoplastic film. The film is used during the fabrication process to contain the belt body material with respect to an outer fabric reinforcement layer. The outer film layer has very poor abrasion resistance. Once in use, the film wears off exposing the fabric layer below.
Particularly relevant prior art is found in U.S. Pat. No. 3,964,328 (Redmond) which discloses a fabric in the preferable form of a stretchable nylon with a thermoplastic layer such as polyethylene bonded to an exterior surface thereof. The fabric is disposed at a peripheral surface of a belt including belt teeth as a wear-resistant fabric and friction modifying reinforcement. The thermoplastic surface has low abrasion resistance and wears away during operation.
What is needed is a belt having a film jacket comprising UHMWPE thermoplastic film. What is needed is a belt having a film jacket comprising UHMWPE thermoplastic film on a sprocket engaging surface. What is needed is a belt having a film jacket comprising UHMWPE thermoplastic film and having high abrasion resistance. The present invention meets these needs.